Fix building on OpenBSD

[brad0]

Replace the check for AI_ADDRCONFIG with AI_V4MAPPED. OpenBSD
has had AI_ADDRCONFIG for 12 years / 23 releases ago. Fill in missing
CMake bits.

• Did you create an Apache Jira ticket? (Request account here, not required for trivial changes)
• If a ticket exists: Does your pull request title follow the pattern "THRIFT-NNNN: describe my issue"?
• Did you squash your changes to a single commit? (not required, but preferred)
• Did you do your best to avoid breaking changes? If one was needed, did you label the Jira ticket with "Breaking-Change"?
• If your change does not involve any code, include [skip ci] anywhere in the commit message to free up build resources.

[Jens-G]

But AI_V4MAPPED and AI_ADDRCONFIG are two different things?

[brad0]

But AI_V4MAPPED and AI_ADDRCONFIG are two different things?

I am very much aware of that.

The comment in the code indicated this was added for OpenBSD. As I said up above we added AI_ADDRCONFIG 12 years ago / 23 releases ago. If you're building with CMake the bits for dealing with AI_ADDRCONFIG are missing anyway.